1. Field of the Invention
The present invention relates to a process for preparing tofu charged into a container, that is useful for preparing what is called "charged Tofu" or "packed Tofu" of the type prepared by the coagulation of soybean milk by heating after soybean milk including a coagulant etc. have been charged into a container and sealed therein. More particularly, the present invention relates to a new effective process for preparing tofu charged into a container when a rapid-acting coagulant such as magnesium chloride is used.
2. Description of the Prior Art
In the preparation of charged tofu, much effort has gone into realizing delayed coagulation reaction so as to avoid the trouble caused by rising viscosity of the soybean milk in the step of transferring the soybean milk including a coagulant to the packaging container to charge it therein, the step of charging it into a packaging container and other steps.
Therefore, there is generally used a delayed-acting coagulant such as .delta.-gluconic lactone (hereafter referred to as G.D.L) which can act slowly as a coagulant in the soybean milk. However, when such a delayed-acting coagulant is used, it is necessary to bring the temperature of the soybean milk down to near room temperature. Moreover, it is generally agreed that tofu prepared by using G.D.L. is less tasty than tofu prepared by using magnesium chloride.
On the other hand, when a rapid-acting coagulant such as magnesium chloride, calcium sulfate etc. is used for preparing tofu, it is known to delay coagulation by using a polyphosphate as a coagulation delaying agent together with said rapid-acting coagulant. But since the coagulation reaction can only be delayed for 1 to 2 minutes by said method, the viscosity of the soybean milk rises after said time and therefore, trouble occurs in the charging procedure.
Japanese Patent Public Disclosure No. 133653/1978 discloses a method in which casein is used as a dispersing and coating agent for coagulant in the form of fine particles. More specifically, in the method disclosed, a coagulant in the form of particles which have been coated with casein is added to soybean milk in order to restrict the solubility rate of the coagulant in the soybean milk, and delayed coagulation of soybean milk is obtained as a result. However, said delayed coagulation effect is inherently limited and therefore, sufficient delayed coagulation effect cannot be obtained by said method.
Furthermore, with conventional methods, various troubles occur in the steps of preparing the tofu charged into a container. At the same time, it is observed that the tofu thus produced loses water, which degrades the quality of the tofu in that it does not have a smooth texture to the tongue.
It is considered that a major cause for this is that the soybean milk is first partially coagulated by the coagulation reaction, the soybean milk thus coagulated is broken during the transferring step, charging step etc., and further coagulation thereafter proceeds by heating.